When completing a well a string of casing, for example, is run in with a one way valve at the lower end known as a shoe. The one way valve is designed to allow flow out through the lower end of the casing such as when cement is delivered and then to act as a check valve to prevent cement that was pumped through the shoe and into the surrounding annular space about the casing from coming back into the casing string. Typically, after pumping in a measured quantity of cement, the cement volume is displaced through the shoe with a wiper plug that is pumped behind the cement. The wiper plug bumps in a landing collar located near the cement shoe. The design of the shoes can vary with some allowing flow in both directions until a ball is landed on a seat and parts are urged to move to convert the action of the shoe to purely a one way valve that allows cement out of the string into the surrounding annulus and prevents the cement from coming back until it can set up in the annulus. The shoe is then drilled out as the well is further extended.
One of the issues that can arise is well control during these operations. The shoe with its one way valve may not be sufficient to hold back an incipient blowout. Additionally as occurred with the Macondo well for BP in the Gulf of Mexico, the blowout preventers may not function if the string is moving them at a rapid velocity. The plugs or darts that could be used to pump down to a secured position at the lower end of the string where pressure differential from above could be used to control the well.
The present invention is a technique for well control in such instances where a valve that is in the casing or other string can be remotely actuated to shut off the string preferably near its lower end by an actuation system that is remotely actuated from preferably a surface location. A rapid response to a developing situation can be initiated to bring a well under control and close off a path to the surface through the string itself. The technique removes any need to try to introduce a ball or plug and land it for well control when time can be of the essence.
Mechanically triggered barriers have been used in applications such as casing drilling where the bottom hole assembly is pulled out through the string for bit replacement or other reasons and a packer is mechanically triggered to close off the string interior as the bottom hole assembly is removed. The closures can be inflatable packers or flappers. Some examples are US Publication 2006/0081401 and U.S. Pat. Nos. 6,343,658; 7,090,039 and 3,545,553.
Those skilled in the art will more readily appreciate other aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawing while recognizing that the full scope of the invention is to be determined from the appended claims.